/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.zhaohg.spark.examples.sql.streaming;

import org.apache.spark.api.java.function.FlatMapFunction;
import org.apache.spark.sql.Dataset;
import org.apache.spark.sql.Encoders;
import org.apache.spark.sql.Row;
import org.apache.spark.sql.SparkSession;
import org.apache.spark.sql.streaming.StreamingQuery;

import java.util.Arrays;
import java.util.Iterator;

/**
 * Counts words in UTF8 encoded, '\n' delimited text received from the network.
 * <p>
 * Usage: JavaStructuredNetworkWordCount <hostname> <port>
 * <hostname> and <port> describe the TCP server that Structured Streaming
 * would connect to receive data.
 * <p>
 * To run this on your local machine, you need to first run a Netcat server
 * `$ nc -lk 9999`
 * and then run the example
 * `$ bin/run-example sql.streaming.JavaStructuredNetworkWordCount
 * localhost 9999`
 */
public final class JavaStructuredNetworkWordCount {

    public static void main(String[] args) throws Exception {
        if (args.length < 2) {
            System.err.println("Usage: JavaStructuredNetworkWordCount <hostname> <port>");
            System.exit(1);
        }

        String host = args[0];
        int port = Integer.parseInt(args[1]);

        SparkSession spark = SparkSession
                .builder()
                .appName("JavaStructuredNetworkWordCount")
                .getOrCreate();

        // Create DataFrame representing the stream of input lines from connection to host:port
        Dataset<Row> lines = spark
                .readStream()
                .format("socket")
                .option("host", host)
                .option("port", port)
                .load();

        // Split the lines into words
        Dataset<String> words = lines.as(Encoders.STRING())
                .flatMap(new FlatMapFunction<String, String>() {
                    @Override
                    public Iterator<String> call(String x) {
                        return Arrays.asList(x.split(" ")).iterator();
                    }
                }, Encoders.STRING());

        // Generate running word count
        Dataset<Row> wordCounts = words.groupBy("value").count();

        // Start running the query that prints the running counts to the console
        StreamingQuery query = wordCounts.writeStream()
                .outputMode("complete")
                .format("console")
                .start();

        query.awaitTermination();
    }
}
